They're pretty self explanatory, but /meclose and /itclose are whisper range and /mefar and /itfar are yell range. /scream is twice the range of the normal yell. /radiow and /radioy effect the eavesdrop range, changing them to whisper or yell range.

There is also @ which will send a message to the admin chat. Only admins can read the admin chat, but regular players can send messages as well if they have need of something.

Along with this, for players there is !report, which you should use to send reports to the admin team that DON'T need to be fixed immediately, such as bug reports.